JP4842562B2 - Current transformer including a combination of partial circuits with a Rogowski type winding forming a complete circuit - Google Patents

Abstract

The turns of Rogowsky type go and return windings of each partial circuit (CB n) are wound in the same direction so as to form a single winding that presents a pair of adjacent electrical terminations. The pairs of electrical terminations of the windings are connected to an acquisition system designated to produce a complete signal representing the primary current of transformer.

Description

  The present invention includes at least two partial circuits, each including a Rogowski-type winding, each of the partial circuits being a complete circuit surrounding the primary conductor of the transformer over 360 degrees. It relates to a current transformer made in the form of an angular part. The winding of each partial circuit is composed of an outward winding and a backward winding that occupy an angular region of the partial circuit. The complete circuit is equivalent to the transformer Rogowski secondary circuit. Thus, the voltage signal measured on this secondary circuit is proportional to the derivative of the current carried by the primary conductor.

  Rogowski coils, also called Rogowski rings, have traditionally been in the form of a conductor wound on a toroidal shaped tool and are made of a non-ferromagnetic material, which results in excellent linearity due to lack of saturation It will be recalled that this coil is given special characteristics. One of the difficulties of measuring the primary current by means of a secondary circuit or conductor in the form of a Rogowski coil results from temperature changes in the coil parameters and can lead to large measurement errors. Furthermore, if the coil is not precisely axisymmetric, the measurement of the derivative of the primary current depends on the position of the primary conductor passing through this ring and also on its orientation. Good axisymmetric is that the conductor winding is wound on the forward path followed by at least two windings, i.e. a similar winding wound on the opposite return path, the forward path and the return path It is known that it is necessary to be constituted by windings having windings wound in the same direction with respect to both the forward path and the return path in order to make the magnetic flux additive to both the windings. Such a double reciprocating winding allows the coil to be unaffected by an electromagnetic field generated by a strong current transmitted by a conductor placed outside the ring.

  State-of-the-art current transformers are known that use partial circuits including Rogowski-type windings. Patent document DE 4 424 368 discloses a square complete coil exhibiting axial symmetry with respect to a primary conductor passing through its center. This coil is composed of four parts, each consisting of a tube coated in a first layer of conductive material, the layers spiraling to form the line that forms the forward winding Etched. The conductive material is coated in an insulating layer and in a second layer of conductive material that is also spirally etched to form the return winding. The four forward lines are connected in series with each other by connecting elements interconnecting the tubes, and so are the return windings. The complete forward line is connected in series with the complete return line, and the complete reciprocating coil created in this way is capable of measuring the voltage induced in the coil by the primary current between the two ends of the terminal. In order to achieve one withdrawal end, it is interrupted at a specific position with respect to one of the tubes.

  This principle of constructing a complete Rogowski-shaped coil from a partial coil in the form of an angular part is also applied in the embodiments disclosed in the patent applications DE 10 161 370 or US 2003 137 388 Al. In particular, an embodiment is described in which a complete coil is constructed by connecting eight semi-annular circuit portions in series. Each part is made up of a printed circuit board (pcb) that forms a half wheel, and a laminate consisting of four plates to form a coil half, including each half of the forward and return windings Has been created. The two half-cycle stacks are separable at two adjacent angular ends to facilitate placement of a complete coil around the primary conductor of the transformer. A series connection of the forward winding and the return winding is located at the first end of the two adjacent angular ends. The two output ends of the complete coil are located at a second angular end adjacent to the first angular end. Thus, while there is no electrical connection between these two adjacent angular ends, nevertheless a double reciprocal winding over 360 degrees to allow the complete coil to exhibit some degree of axial symmetry. Have achieved the line.

To win an electromotive force (emf) signal v _s applied across terminals of the Rogowski coil surrounding a primary conductor over 360 degrees (and generally also be amplified) voltage v _s as measured by according to the following relationship, It is known to depend on the time derivative of the algebraic measurement of the primary current i _p .

Here, S (T) indicates the sensitivity of the coil with respect to the temperature T during the measurement, the constant D is a system-specific amplification coefficient for obtaining the emf v _s. The signal v _s is the image of the indirect primary current (image). Hereinafter, S ₀ indicates the sensitivity of the coil at a specific reference temperature T ₀ . In addition, if the Rogowski coil is wound on an arc-shaped tube, also called a “former”, and extends over an angular section with a specific angle θ, the winding at temperature T ₀ It is possible to define the sensitivity s _{0 of} this part to be equal to S ₀ × θ / 360, where θ is expressed in degrees and S ₀ is wound 360 degrees around the circular forming tool Is the sensitivity of a complete Rogowski-type coil extrapolated by extending it uniformly. For example, if a complete coil is constructed by connecting two semi-annular winding sections in series as shown in patent application DE 10 161 370, the sensitivity s ₀ of each winding section is fully It can be defined as equal to half the coil sensitivity S ₀ .

Nevertheless, in the case of Rogowski-type windings defined over an angle interval of less than 360 degrees, the measured value of the current in the primary conductor is influenced by the position of the conductor with respect to the winding and if the angle It will be observed that if the interval is less than 180 degrees, it is even more strongly affected. The method of the embodiment takes a semi-annular winding arranged perpendicular to the straight primary conductor, so that the conductor is at an equal distance from both ends of the winding. Any displacement, which tends to move away from the primary conductor, even if very small, is a significant increase in the emf measured between the terminals of the winding, assuming that the primary current is uniform over time. Lead to a serious decline. The magnetic field generated by the primary current at a particular point decreases with increasing distance between the point and the primary conductor. As a result, the magnetic flux induced in the winding is reduced by the displacement described above, and thus the measured image of the primary current is attenuated.

  For these reasons and in order to be able to obtain a reliable measurement of the current by means of the Rogowski type winding, it is possible for the winding to show an exact axisymmetric, It is first essential to have a complete winding around the primary conductor. In other words, looping the transformer secondary circuit over 360 degrees is one of the conditions necessary to make it possible to independently measure the position of the primary conductor relative to the secondary conductor. is there. This is because the concept of sensitivity of Rogowski-type windings is relevant to the art only for windings forming a ring or only for a set of windings connected in series to form a complete winding. This is why it appears in general. In known current transformer devices using windings composed of parts of a complete Rogowski coil, such as the transformer shown in patent application DE 10 161 370, for example, each winding is connected to another coil part. Are always electrically connected in series with at least one similar winding formed by, so that these parts together form a complete Rogowski coil that surrounds the primary conductor over 360 degrees .

  In embodiments with two semi-annular windings connected in series, the sensitivity of a full annular winding is actually equal to the sensitivity of a single winding having the same dimensions. Furthermore, providing a series connection is short enough to avoid disturbing the winding uniformity as much as possible in the junction section between the two windings in order to preserve almost perfect axial symmetry, and the measured value is It can remain almost independent of the position of the primary conductor. The relative extra cost implied by such an embodiment based on separable windings compared to conventional windings on a closed support, especially the complete winding around the primary conductor The ease with which it can be installed can be justified. Build a complete Rogowski-type coil without having to allow the two partial coils to be separated from the partial coil and to pass the primary conductor through the loop formed by the complete coil There are also certain situations where can be advantageous.

  Creating a Rogowski-shaped coil from a printed circuit board that is substantially square and provided with a circular cut-out for passing a primary conductor, as known from the patent document EP 0 573 350 Is advantageous. This type of coil presents complete axial symmetry and makes it possible to obtain forward and return windings with a large number of turns in which the magnetic flux of the forward and return windings is additive, As a result, it has a very good sensitivity to the coil with a very good measurement accuracy on the order of 0.1%. The accuracy also remains stable over time. This is because, in practice, it is inherently insensitive to vibrations and temperature changes that can affect the coil. As taught in the patent document EP 0 587 491, in practice, by using a resistor in parallel with the coil output terminal and having a resistance value selected according to various parameters of the coil It is possible to take measurements that are independent of temperature.

  Machines for making printed circuit boards allow boards to be produced in a specific range of sizes. On the date this patent application was filed, there does not appear to be a machine capable of obtaining printed circuit boards with dimensions greater than 700 millimeters (mm). Even if such a machine will be developed in the future, the cost of manufacturing a large sized printed circuit board is a priori, multiple printed circuit boards assembled together to form a large sized printed circuit board. Stays higher than the cost of. Specific measurements of currents made using Rogowski coils, for example for gas-insulated and metallized electrical devices or lines, are formed by transformer secondary coil lines and printed conduction holes. It is necessary for the ring to have an inner diameter that is at least on the same order as this value of 700 mm. For such diameters, it will be observed that it is very advantageous to make the coil on a printed circuit board in order to be able to keep the accuracy of the measurement on the 0.1% grade. This is because the prior art for creating a coil by winding a conductor does not allow a coil to reach this accuracy grade to be produced.

  One technical solution to allow larger size coils to be made from printed circuit boards is to assemble multiple printed circuit boards together in a common plane, each printed circuit board Have angle coil portions etched into them. A first method of interconnecting the angular portions of the complete coil is to connect them in series electrically together via conductors specially constructed for this purpose, ie DE 4 Based on the same principle that the connections shown in 424 368 are made between etched tubes, the windings are connected together in series at each junction between two adjacent plates in the same forward or backward direction. It is essential to connect to. For example, it is possible to assemble four quadrants of a full annular coil together, each quadrant being made from a side square printed circuit board having a length equal to at least half the outer diameter of the annular coil. . Thus, it is possible to make a complete coil using printed circuit board technology up to an outer diameter of about 1,400 mm, which allows the current transformer secondary circuit to be surrounded by current metallized electrical devices. Or exceed the maximum dimensions of the metal coating installed using the line.

  Thus, the secondary circuit of the current transformer implemented by a full annular coil can be installed at ambient temperature, for example around a double metal shell, filled with pressurized insulating gas and passed between Provide a leak-free connection between two metal cases with transformer primary conductors. In one example, the primary conductor is constituted by a conductor of a single-phase metal-coated line. The two shells are connected together by means of a gasket that provides an insulating gas based seal, the gasket being made of a material that provides electrical insulation. This allows the return current flowing into the metal case to pass outside the annular coil, thus ensuring that the current measurement is not affected by the return current.

  Nevertheless, this technology, which essentially consists of connecting the angular portions of a complete coil together in series electrically, uses a coil in the form of a conventional toroidal winding and printed circuit technology. Certain disadvantages may be presented to both created annular coils. First, the connection through the conductor bridge that interconnects two adjacent portions of the complete coil, to some extent, hinders the uniformity of the winding distribution in the junction section between the windings. This can be seen especially in FIG. 3 of patent document DE 10 161 370, for example. For angle sections implemented in the form of printed circuit board quarters, to maintain almost perfect uniformity of the winding distribution in a complete Rogowski coil, in order to maintain measurement accuracy within 0.1% grade It is necessary to provide a very short connection. Furthermore, the electrical and mechanical joint section between two adjacent printed circuit board quadrants constitutes a weak section when subjected to vibration and expansion to which such quadrants are exposed. Even if the quadrant is mounted on a relatively flexible element, such as an element made of rubber, to limit the amplitude and stress of vibration at the joint between the quadrants, the quadrant If the conductive bridges interconnecting the printed circuits of the body are provided in a rigid manner, it is possible to avoid the risk of destruction in those bridges, and therefore a flexible conductive bridge It is generally necessary to provide

  Nevertheless, the difficulty in obtaining an electrical connection between two adjacent printed circuit board quadrants that are mechanically reliable and that do not interfere with the measurement as much as possible is the flexible conductive bridge technology. It can be overcome by using especially. It is therefore possible to obtain a large sized complete annular Rogowski-shaped coil made of printed circuit board quadrants, which is a single printed circuit of the same size and taught in the patent document EP 0 573 350 Of course, it is assumed that a machine is available that is electrically equivalent to a coil that uses the same printed circuit board as the board and that allows printed circuit boards of such size to be made. The two electrical terminations of a complete Rogowski coil are preferably located at one end of the coil quadrant next to the junction with the adjacent quadrant, so that the junction is crossed by a conductive bridge. Only the unjoined joints.

In view of the above technique using a Rogowski-type coil quadrant specifically for printed circuit board technology embodiments taught by patent document EP 0 573 350, the ring formed by the complete coil of the current transformer is gas insulated. In practical applications to current transformers for metallized electrical devices, it is necessary to consider the fact that it can have a diameter typically greater than 700 mm. Thus, the total number of turns (each formed by two opposite line sections and two plated through holes in the printed circuit board) can be very large for a complete Rogowski coil. At this stage, it will be recalled that the total sensitivity S ₀ of a large diameter Rogowski coil is hardly different from the total sensitivity of a coil with the same density of turns but of a smaller diameter. The increase in sensitivity due to the larger number of turns is balanced because the magnitude of the magnetic field is reduced by the coil further away from the primary conductor whose current is to be measured.

Thus, even for large diameter coils, parasitic surge voltage signals that can interfere with the emf signal induced in the coil are of relatively large amplitude. This is because the total sensitivity S ₀ is actually independent of the coil diameter. The interference signal is caused by a high frequency current in the line where the primary current i _p is being measured by a transformer. Since the emf signal is proportional to the derivative of the primary current i _p , any high frequency disturbance affecting the primary current will inevitably lead to a voltage surge at the secondary winding terminal of the transformer. Subsequently, the interference voltage surge signal is acquired and processor suitable for generating a corrected signal v _s (this signal is usually amplified) which is an image of the corrected primary current signal filtered high frequency current disturbance. Must be processed by the department.

  Due to its relatively large amplitude, the interference voltage surge signal can be difficult to process when correcting the measurement signal, and this therefore leads to less accurate measurements. Even when high-performance signal correction processing is applied to the emf signal across the terminals of the Rogowski coil to obtain very high measurement accuracy, this is a situation where the voltage surge interference signal is of a smaller amplitude In general, it includes an increased cost compared to getting exactly the same order.

The main object of the present invention is to provide a current transformer whose secondary circuit includes a large diameter complete Rogowski coil, which is very much related to axisymmetric about this complete coil. A configuration for a transformer secondary circuit that is created from multiple angle coil parts that are mechanically assembled with excellent uniformity while functioning to limit the amplitude of the interference voltage surge signal to be processed Also have. A more detailed object of the present invention is to implement a complete Rogowski-type coil printed circuit board technology, which is large diameter while omitting any conductive bridge between adjacent partial printed circuit board coils making up a complete coil. Providing a form, this embodiment allows accuracy to be achieved with at least 0.1% grade with excellent temperature stability.
DE 4 424 368 DE 10 161 370 US 2003 137 388 Al EP 0 573 350 EP 0 587 491

  For this purpose, the present invention comprises at least two subcircuits, each comprising a Rogowski winding, each of the subcircuits being an angular portion of a complete circuit that surrounds at least one primary conductor of the transformer over 360 degrees. The complete circuit has the function of a Rogowski secondary circuit for the transformer, and the winding of each partial circuit is a current constituted by the forward winding with the return winding extending over the angular region of the partial circuit. A transformer, for each subcircuit, the forward and return windings are electrically connected in series so that both form a single winding that provides a pair of adjacent electrical terminations. Featuring windings wound in the same direction, a pair of electrical terminations of the windings are connected to an acquisition system designed to produce a complete signal that is an image of the primary current of the transformer A current transformer Provide.

Thus, a complete circuit constructed by concatenating several N subcircuits presents the same number N of electrical terminations. As described below, the emf signal V _{s (n)} measured between the terminals of each partial circuit has the following relationship at a specific reference temperature T ₀ :

Is transmitted to a summation acquisition system (generally including amplification) designed to recreate a complete signal V _s that satisfies Here, K represents the overall amplification factor of the additive acquisition system, and S ₀ represents the sensitivity of the equivalent complete circuit. The following describes how the resistance value of the resistor that defines the overall amplification coefficient can be parameterized so that the coefficient is insensitive to temperature changes. S ₀ to obtain a configuration equivalent to the configuration described in patent EP 0 573 350 where the complete coil presents only two electrical terminations to obtain the emf signal that constitutes the image of the primary current It will be observed that it is equal to the sensitivity of a complete coil as constructed by connecting the windings of the partial circuits in series.

In the current transformer of the present invention, and when all of the partial circuits are the same, the sensitivity S ₀ of the fully equivalent circuit is equal to the sensitivity s ₀ of the partial circuit multiplied by the number N of partial circuits. Therefore, the above equation (2) becomes

Thus, it is possible to determine the primary current of the transformer by integrating over time the complete signal v _S measured for the Rogowski-type secondary circuit.

  Preferably, the pair of electrical terminations of the partial circuit is placed at one of the two angular ends of the partial circuit, the forward and return windings each advance over the angular region of the partial circuit, and the other angle The ends are electrically connected in series in series. This arrangement of terminals at one angular end of the partial circuit is especially useful for using two relatively short shielded cables of the same length to connect both circuits to the signal acquisition system Allows the terminals of the circuit to be placed side by side. To minimize the interference signals that can be generated in the cabling due to the strong electromagnetic field due to the current carried in the primary conductor adjacent to the current transformer and to classify those interference signals to the 0.1% It has been found that it is important that both cables be relatively short and of the same length in order to keep them low to a level that does not interfere with accuracy.

  In a preferred embodiment of the current transformer of the present invention, each partial circuit is embodied by a flat or curved printed circuit board having a set of metal lines on each of its two sides, and a set of lines. Are electrically connected to another set of lines via plated through holes that pass through the printed circuit board to form the windings of the partial circuit.

  In another advantageous embodiment of the current transformer of the invention, one of the two terminations of the windings of each subcircuit is electrically connected to a common reference potential, while the other termination is a feedback loop. Is electrically connected to the input of an acquisition system that provides an amplification function that includes at least one operational amplifier. Advantageously, each input of the acquisition system is connected through a resistor of a resistance value selected such that the voltage signal measured at the output from the acquisition system is independent of the temperature change of the transformer secondary circuit. Connected to operational amplifier input.

  The invention, features of the invention, and advantages of the invention are described in more detail below with reference to the following drawings.

In FIG. 1, a partial circuit CB _n for the current transformer of the present invention is schematically shown in the form of a planar annular quadrant made using printed circuit board technology. A method for creating a printed circuit board Rogowski winding is known from the patent document EP 0 573 350, in which straight metal lines provided on two sides of the printed circuit are extended. This allows it to be placed on a radius that passes through the center O of the annular quadrant. The angular region θ _n of the partial circuit is in this case so that a complete circuit is formed by connecting four identical partial circuits together in a common plane to form the secondary conductor of the Rogowski transformer. Is equal to 90 degrees. Hereinafter, the term “secondary circuit” is used to designate the secondary conductor of the current transformer of the present invention, especially when made using printed circuit board technology. Using current machines for manufacturing printed circuit boards, using rectangular printed circuit boards that are about 700 mm long in maximum dimensions, partial circuits that occupy an annular quadrant up to an external radius of up to about 500 mm Can be created.

Thus, the partial circuit CB _n is in this case formed by a quadrant of an annular secondary circuit as described in patent EP 0 573 350. Nevertheless, the partial circuit CB _n is not electrically identical to the quadrant as obtained by simply cutting out the printed circuit that makes up the Rogowski coil in the state-of-the-art technology detailed above. . As can be seen in FIG. 1 (b), each subcircuit CB _n has an adjacent electrical termination that forms two ends of a single continuous winding C _n at the first annular end E _1n . Of pairs T _1n and T _2n . The forward and return windings covering the angular area of the partial circuit, respectively C _n0 to C _n1 are electrically connected in series at the second angular end E _2n of the circuit, so that the coil C _n is terminated T It is continuous between the two terminals constituted by _1n and T _2n. The metal line shown in the continuous line is formed on one side of the partial circuit, while the line shown in the interrupted line is formed on the other side of the circuit.

As can be seen in FIGS. 1 (a) and 1 (b), the two angular ends E _1n and E _2n of the _subcircuit CB _n for the current transformer of the present invention are connected to other _subcircuits . It does not include any conductive bridge for. Because the winding C _n partial circuit CB _n, because independent of the winding of the other partial circuits of the circuit is completely over 360 degrees. As shown in FIG. 1 (b), the emf signal v _{S (n)} can be measured between terminals constituted by two terminations T _1n and T _2n of each partial circuit.

To simplify the diagram of FIG. 1 (a) and 1 (b), forward and backward winding respectively C _n0 and C _n1 is the conductor wire continuous winding C _n is wound around a wheel It is shown as if it was formed. Nonetheless, this method of winding is in fact the current transformation of the present invention, even though this method meets the need to avoid crossing the wires between the forward and return windings. It is not adapted to the partial circuit for the vessel. As shown in FIG. 1 (a), the forward winding C _n0 is not wound in the same direction as the return winding C _n1 . More specifically, the winding of the forward winding C _n0 proceeds in a counterclockwise direction for the observer wound to the right in FIG. 1 (a), while the winding of the return winding C _n1 is Proceeding clockwise for the same observer. Thus, this method of winding cannot allow the magnetic flux to be additive between the forward and return windings, and does not allow the specific circuit of the subcircuit to be used in the current transformer of the present invention. Other methods must be used to create the winding. For example, using printed circuit board technology, with reference to the configuration of the metal line shown in FIG. 2b of patent document EP 0 573 350, with alternating forward and return windings described in that document It is possible to adopt a winding method.

  FIG. 2 is a schematic perspective view showing a complete annular circuit CB constructed by connecting four partial circuits that are created using printed circuit board technology. The complete circuit constitutes the secondary circuit of the current transformer of the invention, and the primary conductor of the transformer is in this case preferably constituted by the rod 10 of the axis Z passing through the ring in the center O of the ring, preferably vertically. Has been. The four partial circuits constitute the same quadrant with alternating faces A and B mounted on a common planar annular frame 15, so that the adjacent angular ends of the partial circuits are held next to each other Yes. A fastener 16 having elastic return characteristics is provided to hold together two adjacent angular ends. In order to avoid any loose or excessive stress appearing between two adjacent subcircuits during a temperature change, the expansion coefficient of the frame 15 is preferably substantially equal to the expansion coefficient of the substrate of the printed circuit board.

Thus, CB ₄ four identical partial circuits CB ₁ is assembled on the annular frame 15, completely circuit, such as by means of a circular hole formed through a radial projection from the outer edge of the printed circuit Held on the frame. Here, these holes must be provided in order to pass the corresponding cylindrical embedding bolts with little play, these embedding bolts are fixed on the frame, and the two cylindrical embedding bolts are It can be sufficient to mount one partial circuit on top. In this embodiment of a full ring circuit composed of identical partial circuits, two adjacent partial circuits have alternating A and B planes when viewed from the same side of the ring, so that these partial circuits Two individual pairs of terminals are arranged side by side. The advantages of this arrangement will be described below with reference to the embodiment shown in FIG.

Schematically they are shown in Figure 2a a partial circuit CB ₁ complete circuit CB shown in FIG. The two terminals T ₁₁ and T ₂₁ of the printed circuit are in this case located on the face A of the single layer 3 of the substrate forming the printed circuit board at the first angular end E ₁₁ of the annular quarter. These two terminals can be individually connected to two cables terminating in the acquisition system for measuring emf vs _{s (1)} of circuit CB ₁ , for example by soldering To do so, these two terminals are generally separated by a distance of a few tenths of a millimeter. Preferably, these two terminals are constituted by plated through hole passing through the thickness of the plate 3, and constitute the terminal T ₁₁ and T ₂₁ of the winding of the partial circuit CB _1. Thus, the soldering for the two above-mentioned cables can be performed from either of the two sides A and B of the circuit. In particular, the partial circuit CB ₂ seen in Figure 2 is designed to be identical to the circuit CB ₁ , but the soldering of the two cables to measure the circuit's emf vs _{s (2)} is a circuit aspect. Done on B. In this way, pairs of cables from partial circuits can all be installed on the same side of the complete circuit CB, for example on the side as seen in FIG.

In FIG. 2b, the surface A of the secondary annular end E ₂₁ of the partial circuit CB ₁ of Figure 2a is shown schematically shows a set 31 of the metal lines on the surface. The lines of the forward winding C ₁₀ and the return winding C ₁₁ are interleaved and are almost parallel to each other, and therefore increase the line density in order to give high sensitivity to the windings of the partial circuit. Is possible. The surface B of this secondary angle end E ₂₁ is schematically shown in FIG. 2c together with its own set 32 of metal lines. The plated conduction hole 6 passes through the circuit board at the end of the line and is provided to create a Rogowski-type winding winding as described in patent document EP 0 573 350 It serves to interconnect line to C ₁₀ or return winding C _11.

FIG. 3 is an exploded schematic partial view of a secondary circuit that compares two complete circuits placed parallel to each other. For simplicity reasons, only partial circuits CB _n and CB _{n + 4} are shown. Based on the same principle as described in Patent Document EP 0 573 350, and referring to FIG. 3 of the same document, the superposition of a plurality of Rogowski coils is corresponding to all secondary circuits. It is advantageous for increasing the sensitivity. In this case, each complete coil is attached so as to be held in place by a support post fixed to the annular frame 15. An annular metal shield 17 is inserted between the two coils and serves as a support to ensure that the partial circuit CB _{n + 4} is flat. This shield functions in a capacitive manner with reference to the main support formed by the annular frame 15 which is also made of metal in this case. The two inserted metal frames 15 and 17 are aligned and held on the shaft by a column fixed to the frame 15. Therefore, it is possible to construct a laminate of alternating layers of Rogowski coils made of printed circuit board and made of metal shield 17. Advantageously, a mylar sheet can be inserted between each side of the shield 17 and the printed circuit of the complete coil pressed against this side.

FIG. 4 is a schematic partial view of another secondary circuit including two complete circuits arranged parallel to each other. In this case, except for the capacitive screen which has been removed, this secondary circuit is electrically equivalent to the secondary circuit of FIG. Between each partial circuit CB _n and the partial circuit CB _{n + 4} inserted above it, a layer 5 of resin or some other insulating material is inserted, and each group of inserted partial circuits has two It is possible to form a laminate composed of a printed circuit board. The material of the insulating layer 5 separating the two printed circuit boards must have an expansion coefficient that is close to or equal to the expansion coefficient of the printed circuit board substrate, and also the printed circuit board It is also possible to optionally have a function of integrally connecting the two. Although only one group is shown in the figure, it should be understood that the secondary circuit is composed of four groups of insertion subcircuits mounted on the same annular frame 15.

FIG. 5 is a schematic partial view of another secondary circuit of the current transformer according to the invention, which in this case is constituted by a single complete coil. Each partial circuit of the complete coil includes two inserted printed circuit quadrants separated by a layer 5 of insulating material. In this case, each printed circuit board 3 or 4 forming the quadrant is etched in such a manner that the winding formed by the printed circuit board is constituted by a single forward or return path winding. For example, if the forward winding is etched on the printed circuit board 3 starting from the terminal formed by the termination T _1n at one angular end of the quadrant, the return winding etched on the plate 4 In order to connect with, an electrical connection is made at the opposite angular end. The lines of the return winding must be arranged so that the winding direction of the return path is the same as that of the forward winding, so that the individual magnetic fluxes of the forward and return windings are added. The terminal T _2n of the return winding can be placed very close to the terminal T _1n and is separated from it by the thickness of the insulating layer 5. This thickness is preferably limited to a few tenths of a millimeter.

  FIG. 5a is a schematic plan view of this partial circuit as viewed along the direction Y indicated by the dashed arrows. In the known method, two sets of lines 41 and 42, respectively, etched on the two faces of the plate 4 are interconnected by plated through holes that pass through the thickness of the printed circuit board. . The same applies to the two sets of lines 51 and 52 respectively etched on the two faces of the plate 3. The thickness of the insulating layer 5 is preferably thinner than either the printed circuit board 3 or 4.

FIG. 6 is a perspective view of another current transformer of the present invention having a specific configuration. The secondary circuit of the transformer is formed by a complete tubular annular circuit constituted by connecting four partial circuits forming the same quadrant, and this complete circuit is fixed to the annular frame 15. Accordingly, each printed circuit board is bent so that the axis of symmetry has the shape of the angular portion of the tubular ring that substantially coincides with the axis Z of the primary conductor 10 of the transformer. As can be seen in FIG. 6a, the metal lines on each of the partial circuit faces A and B are parallel to the axis of symmetry. Each angular end E _1n or E _2n of the partial circuit is located along a straight edge of the bent printed circuit board forming the circuit.

An electric circuit diagram of the current transformer of the present invention is shown in FIG. By way of example, the transformer includes a complete secondary circuit CB corresponding to that shown in FIG. 2 and constructed by concatenating four identical subcircuits with alternating surfaces. The secondary circuit of the transformer functions in this case both for summing and for amplification, and for this purpose is electrically connected to an acquisition system 7 including an operational amplifier 8 with a feedback loop Has been. For each partial circuit CB _n, one of the two terminals T _1n or T _2n windings while being connected to a common reference potential G, the other terminal is electrically connected to the input E _n acquisition system 7 ing.

For example, the terminal T ₁₁ of the partial circuit CB ₁ is connected to the ground at the ground potential, and the other terminal T ₁₂ is connected to the resistor R ₁ at the input of the acquisition system 7. As schematically shown in the figure, the windings of the respective partial circuits CB _n have an additive magnetic flux between the windings C _n0 and C _n1 of the outgoing path and the returning _path. It must be wound in the same direction for both paths on the return path. For example, when traveling from the terminal C ₁₁ to terminal C _12, forward winding C ₁₀ and return winding C ₁₁ it can be seen that their winding is wound in the same direction, which is counterclockwise.

Advantageously, the two terminals T _1n and T _2n of the _subcircuit alternate with respect to the two terminals T _{1n + 1} and T _{2n + 1} of the adjacent _subcircuit , respectively, and are connected to the ground and the input of the acquisition system 7, respectively. is 1 bright and early connection of the E ₄ from E _1. In this way, the output voltage signals v _{s (1)} to v _{s (4)} of the partial circuits are added in phase by the acquisition system. It is important to avoid these signals being summed in reverse phase. This is because the voltage signal v _s measured at the output terminal 11 of the acquisition system is because substantially zero. In this configuration, the polarity of the connection between the terminals of the subcircuit and the input of the acquisition system is alternated because the subcircuits are assembled together as shown in FIG. 2 with their faces alternating in pairs. It will be necessary. Therefore, in-phase addition of voltage signals is applied to the inverting input 9 of the operational amplifier 8.

The summing and amplification principle shown by the circuit of FIG. 7 can also be applied when the current transformer has multiple p complete circuits arranged in parallel to each other. Such an arrangement of the complete circuit is described above with reference to FIGS. Input 9 of the operational amplifier 8 is connected through a resistor R ₁ in each one of the terminals of the partial circuit CB _n constituting the p number of complete circuits. If if it contains the complete circuit of four partial circuits, there is a 4p inputs resistor R ₁ to the acquisition system 7.

As shown below, the signal v _s measured at the output from the acquisition system 7 is subject to temperature changes, provided that the resistance value of each input resistance R ₁ of the acquisition system 7 satisfies the following relationship (9): Become independent.

It has been shown above that the sensitivity s of the partial circuit is defined such that the emf signal v _s measured between the terminals of the partial circuit satisfies the following relationship:

  Furthermore, the internal resistance value r of the winding of the partial circuit varies linearly with the temperature T of the partial circuit in the application of the following relationship, which is well known per se.

Here, ΔT = T−T ₀ , β is a temperature coefficient with respect to the resistivity of the material constituting the winding, and T ₀ is a reference temperature. For example, if the material is copper, β is approximately 3,900 parts per million (ppm / ° C.).

  Similarly, the sensitivity s of the partial circuit varies linearly with the substrate temperature T. This is because the expansion of the substrate increases the winding section of the partial circuit, and the section is proportional to the thickness of the substrate. This relationship is described as follows.

Here, α _z is a coefficient of linear expansion of the substrate in a direction perpendicular to the surface of the substrate. In the embodiment shown in FIG. 2, this direction corresponds to the axis Z. The coefficient α _Z ranges from 40 ppm / ° C. to 60 ppm / ° C., depending on the material used.

  The current at the inverting input 9 of the operational amplifier 8 is zero assuming that the amplifier is ideal, so Kirchhoff's law leads to the following relationship:

Here, N is the number of partial circuits. Given relationship (4), we get

  Since N partial circuits are assumed to be the same and at the same temperature T, all the windings have the same internal resistance r and the same sensitivity s satisfying the relations (5) and (6) at the temperature T, respectively. It can be assumed. Therefore, the relationship (7) is as follows.

If the value R ₁ is chosen to satisfy the following relationship:

  It can be seen that the relationship (8) can be described as follows.

  Therefore, referring to the relationship (2), the overall amplification coefficient K of the addition acquisition system 7 satisfies the following relationship.

Or, indeed, replacing R ₁ as a function of relation (9) yields:

In absolute terms, the resistance values R ₁ and R ₂ are not completely stable with changes in temperature. In practice, however, first, the temperature coefficient of each resistance value can be selected to be very small (e.g., less than 5 ppm / ° C for resistance values made of NiCr), and secondly, Slight changes in the individual resistance values R ₁ and R ₂ as a function of temperature

Occur together and in the same direction so that they can be considered completely stable with respect to temperature. Therefore, the coefficient K, and, therefore, the measured signal v _s is independent of the change in temperature. Thus, the signal v _s is a very accurate image of the current i _p carried by the primary conductor 10.

  FIG. 8 is an electrical circuit diagram of the current transformer of the present invention in which two complete circuits are arranged in parallel with each other as described above with reference to FIGS. Each complete circuit is a circuit of the type described above with reference to FIG. It should be understood that the principles shown for creating an electrical connection between the transformer secondary circuit and the sum acquisition system can be applied to a number p of complete circuits greater than two.

The summing acquisition circuit 7 'includes two stages of amplification. The first amplification stage in this case comprises two operational amplifiers 8 each handling half of the emf signal v _{s (n)} of the partial circuit. Thus, the first amplification stage is composed of two identical amplification subassemblies 71 and 72, each similar to the circuit of acquisition circuit 7 shown in FIG. The output from each amplifier 8 in the first stage is connected to a second summing stage designed to generate a complete signal (v _s ) that is an image of the primary current. This second stage includes an operational amplifier 8 ′ with a loop for amplifying the sum of the signals generated by the first amplification stage.

The main advantage of this acquisition circuit 7 'relates to the arrangement of the terminals of the current transformer subcircuit. Whatever the number p of complete circuits, a group on the opposite side of the two diameters of the terminals is obtained. For example, the terminals of the partial circuits CB ₁ , CB ₂ , CB ₅ , and CB ₆ are close to each other and form a first group, while the terminals of the remaining partial circuits are on the opposite side in diameter Form a second group. Each group of terminals is electrically connected to an amplification subassembly 71 or 72, and if each subassembly 71 or 72 is placed next to its own group of terminals, it constitutes the cabling. The length of the same length cable can be particularly shortened. Thus, effective electromagnetic shielding of each cable assigned to a group of terminals, and also each amplification subassembly, can be achieved without great difficulty, so that from the input E ₁ of the acquisition system 7 ′ The two groups of signals v _{s (n)} in each of E ₄ and E ₅ to E ₈ are not disturbed by the electromagnetic field due to the current flowing in the primary conductor adjacent to the current transformer.

First signal v ₇₁ and v ₇₂ produced by amplifier stage satisfy the following relationship.

Complete signal v _s satisfy the following relationship.

If the sensitivity S of the complete circuit and the internal resistance r of the partial circuit satisfy the following relationship,

Relationship (9) it becomes possible again to select the R ₁ to meet, therefore, the output voltage v _s of the acquisition system 7 'becomes independent of the temperature T of the complete circuit.

  Therefore, the relationship (14) is as follows.

The resistance values R ₃ and R ₄ can be selected to be the same so that the second amplification stage simply adds the output voltages from the first two stages 71 and 72. Therefore, the above relationship can be described as follows.

Comparing relations (10) and (15) clearly shows that the sensitivity equivalent to two identical complete circuits connected in parallel is equal to twice the sensitivity S ₀ of one complete circuit. In addition, the advantages with a plurality of complete circuits disposed parallel to each other is also to enable an increase in the signal-to-noise ratio for the output signal v _s acquisition system.

  The signal-to-noise ratio for p identical perfect circuits is √p times greater than the signal-to-noise ratio for a single perfect circuit.

It is not essential to use an operational amplifier for the signal acquisition system provided by the current transformer secondary circuit of the present invention. The sensitivity of each subcircuit of the secondary circuit is the voltage signal between the terminals of the resistor R ₁ satisfying the relationship (9) and interconnecting two adjacent electrical terminations T _1n and T _2n of the _subcircuit v It may be sufficient to obtain _{s (n)} . Thus, N signals v _{s (n)} can be acquired separately, each of which provides (with amplification) to recreate the full circuit secondary signal formed by the N subcircuits. (And / or without) can be transported to an addition system. For example, each voltage signal v _{s (n)} between the terminals of resistor R ₁ can be obtained by an analog / digital converter, and then the digital signal can be placed in a summing system that can be placed away from the secondary circuit. It is conveyed optically.

It is also possible to omit the operational amplifier 8 ′ in the second amplification / addition stage of the acquisition system 7 ′ shown in FIG. Analog / digital converter can be provided on the output from each of the two amplifier subassembly 71 and 72 of the first amplifier stage, followed by two digital signals digital to recreate a signal v _s For example, it can be transmitted optically to the summing system.

Thus, the current transformer of the present invention can be used to detect any residual current. FIG. 9 is a diagram of a transformer in which a secondary circuit is formed by assembling three partial circuits together to surround three primary conductors 10A, 10B, and 10C of a three-phase line. Subsequently, the three outputs of the partial circuits CB ₁ to CB ₃ are obtained in order to obtain an image of the total primary current i _p , i.e. an image of the residual current constituted by the vector sum of the three currents in the three primary conductors. The voltages v _{s (1)} to v _{s (3)} should be added in phase by the acquisition system. Without any fault current, this vector sum is zero, thus producing a voltage signal whose output from the acquisition system is substantially zero. However, if an earth fault occurs, the vector sum is no longer zero, thus allowing the acquisition system to obtain an image of the residual current. Although the accuracy of the measurement system is inferior to that of the fully circular annular coil described above, the measurement system can be satisfied without difficulty. This is because measuring the residual current usually functions to trigger a protection operation. Under such circumstances, it is not necessary to have a measurement accuracy in the 0.1% grade.

FIG. 4 is a partial circuit diagram of the current transformer of the present invention in the form of a planar annular quadrant made using printed circuit board technology, with (a) enlarging the first angular end of the partial circuit. FIG. 5B is an enlarged view showing a second angle end portion of the partial circuit. Schematic of the current transformer of the present invention comprising a complete annular circuit constructed by connecting four partial circuits having alternating surfaces and forming the same quadrant constituting the secondary circuit of the transformer FIG. FIG. 3 is a diagram of a partial circuit forming one of the quadrants constituting the complete circuit of FIG. FIG. 2b is a diagram showing one face of one angular end of the partial circuit of FIG. 2a and showing a set of metal lines on the face. FIG. 3 is a view showing another surface of the annular end of the partial circuit shown in FIG. 2b together with a set of metal lines thereof. FIG. 3 is a schematic partial view of the secondary circuit of the current transformer of the present invention including two complete circuits placed parallel to each other. It is a typical fragmentary view of the other secondary circuit of the current transformer of the present invention. FIG. 6 is a schematic partial view of another secondary circuit of the current transformer of the present invention, which is composed of a single complete circuit, each of which includes two superimposed printed circuit boards. FIG. 6 is a schematic plan view of the partial circuit shown in FIG. 5 provided with a support portion. FIG. 3 is a schematic perspective view of the current transformer of the present invention including a complete tubular annular circuit constructed by connecting four partial circuits forming the same quadrant. FIG. 7 is a diagram of two faces of a partial circuit forming one of the quadrants constituting the complete circuit of FIG. FIG. 4 is an electrical schematic of the current transformer of the present invention including a complete circuit constructed by connecting four alternating identical partial circuits and further including a summing acquisition system. FIG. 2 is an electrical schematic of the current transformer of the present invention that includes two complete circuits arranged in parallel to each other and further includes a summing acquisition system having two stages of amplification. FIG. 4 is a diagram of the current transformer of the present invention applied to detecting any possible residual current in a three-phase line.

Explanation of symbols

A, B side
_{C 1, C 2, ...,} C n, ..., C N Rogowski coil
C _n1 return coil
C _n0 outbound coil
_{CB 1, CB 2, ...,} CB n, ..., CB N partial circuits
E _1n , E _2n angle end
G Common reference potential
O center
T temperature
T _1n , T _2n electrical terminals
Z axis θ _n Angular region
i _p primary current
v _s complete signal
7, 7 'acquisition system
8,8 'operational amplifier
9 inputs
10, 10A, 10B, 10C Primary conductor
15 frames
16 Fastener
31, 32, 41, 42, 51, 52 Metal track

Claims (11)

At least two partial circuits (CB ₁ , CB ₂ , ..., CB _n , ... each containing a Rogowski winding (C ₁ , C ₂ , ..., C _n , ..., C _N ) .. , CB _N ), each of said subcircuits being made in the form of an angular portion of a complete circuit (CB) that surrounds at least one primary conductor (10, 10A, 10B, 10C) of the current transformer over 360 degrees and has the full circuit has the function of Rogowski type secondary circuit for the transformer, the winding (C _n) is the angle region (theta _n of the partial circuit (CB _n) of each partial circuit (CB _n) ) _Extending along the return winding (C _n1 ) and the forward winding (C _n0 ) for each partial circuit (CB _n ), the forward and return windings (C _n0 , C _n1 ) are electrically connected in series and both are wound in the same direction to form a single winding (C _n ) that provides a pair of adjacent electrical terminations (T _1n , T _2n ). The winding (C _n ) A pair of electrical terminations (T _1n , T _2n ) is an acquisition system (7, 7 ′) designed to produce a complete signal (v _s ) that is an image of the primary current (i _p ) of the current transformer. Connected to
A pair of electrical terminations (T _1n , T _2n ) of the partial circuit (CB _n ) are arranged at one of the two angular ends (E _1n , E _2n ) of the partial circuit, and the forward and return windings (C _n0 , C _n1 ) each extend along the angular region (θ _n ) of the partial circuit (CB _n ) and are electrically connected in series at the other angular end of the partial circuit. And
Each partial circuit is created in the form of a flat or curved printed circuit board with multiple sets (31, 32) of metal lines on each of the two faces, and one set (31) of lines is said part Electrically connected to the lines of the other set (32) via plated conduction holes (6) that pass through the printed circuit board to form the winding (C _n ) of the circuit (CB _n ). ,
The printed circuit board includes a substrate layer of constant thickness between two sets (31, 32) of metal lines, and the first half of each set of lines is for the forward winding (C _n0 ) While the other half is used for the return winding (C _n1 ) of the partial circuit,
Each subcircuit is in the form of a flat ring angle to form a complete ring circuit (CB), and each set of metal lines (31, 32) on the printed circuit board is substantially straight The center of the ring (O) is created with a track extending along a radius when extended through an axis (Z) perpendicular to the ring,
The complete circular circuit (CB) is made up of at least four identical partial circuits whose faces (A, B) on one side of the ring alternate in pairs, so that the first partial circuit A pair of electrical terminations (T _1n , T _2n ) of the winding is arranged next to the other pair of one electrical termination of two partial circuits adjacent to the first partial circuit Characteristic current transformer. Each partial circuit (CB ₁ , CB ₂ , ..., CB _N ) is made from two printed circuit boards (3, 4), and each board has one set (41, 42) on each of its two faces. 51, 52) metal lines of one set (41; 51) on one printed circuit board, the forward winding (C _n0 ) or return winding of the partial circuit (CB _n ) Characterized in that it is electrically connected to another set (42; 52) of lines on the same printed circuit board via plated conduction holes to form any of the lines (C _n1 ) The current transformer according to claim 1. At least two partial circuits (CB ₁ , CB ₂ , ..., CB _n , ... each containing a Rogowski winding (C ₁ , C ₂ , ..., C _n , ..., C _N ) .. , CB _N ), each of said subcircuits being made in the form of an angular portion of a complete circuit (CB) that surrounds at least one primary conductor (10, 10A, 10B, 10C) of the current transformer over 360 degrees and has the full circuit has the function of Rogowski type secondary circuit for the transformer, the winding (C _n) is the angle region (theta _n of the partial circuit (CB _n) of each partial circuit (CB _n) ) _Extending along the return winding (C _n1 ) and the forward winding (C _n0 ) for each partial circuit (CB _n ), the forward and return windings (C _n0 , C _n1 ) are electrically connected in series and both are wound in the same direction to form a single winding (C _n ) that provides a pair of adjacent electrical terminations (T _1n , T _2n ) . The winding (C _n ) A pair of electrical terminations (T _1n , T _2n ) is an acquisition system (7, 7 ′) designed to produce a complete signal (v _s ) that is an image of the primary current (i _p ) of the current transformer. Connected to
A pair of electrical terminations (T _1n , T _2n ) of the partial circuit (CB _n ) are arranged at one of the two angular ends (E _1n , E _2n ) of the partial circuit, and the forward and return windings (C _n0 , C _n1 ) each extend along the angular region (θ _n ) of the partial circuit (CB _n ) and are electrically connected in series at the other angular end of the partial circuit. And
Each partial circuit is created in the form of a flat or curved printed circuit board with multiple sets (31, 32) of metal lines on each of the two faces, and one set (31) of lines is said part Electrically connected to the lines of the other set (32) via plated conduction holes (6) that pass through the printed circuit board to form the winding (C _n ) of the circuit (CB _n ). ,
The printed circuit board includes a substrate layer of constant thickness between two sets (31, 32) of metal lines, and the first half of each set of lines is for the forward winding (C _n0 ) While the other half is used for the return winding (C _n1 ) of the partial circuit ,
Each printed circuit board is in the form of an angular portion of a tubular ring whose axis of symmetry coincides with the axis (Z) of the primary conductor of the current transformer, and the metal line of the printed circuit is the primary conductor of the primary conductor. Ri parallel der said axis (Z),
The complete circular circuit (CB) is made up of at least four identical partial circuits whose faces (A, B) on one side of the ring alternate in pairs, so that the first partial circuit A pair of electrical terminations (T _1n , T _2n ) of the winding are arranged next to the other pair of one electrical termination of two partial circuits adjacent to the first partial circuit <br>/> current transformer you wherein a.   The complete circuit is mounted on a flat frame (15) with at least one primary conductor (10) of the current transformer passing vertically and a fastener (16) having elastic return characteristics. 2. A current transformer as claimed in claim 1, wherein said current transformer is provided to hold adjacent angular ends of said printed circuit board relative to each other. For each partial circuit (CB _n ), one of the two electrical terminations (T _1n , T _2n ) of the winding is electrically connected to a common reference potential (G), while the other termination is Characterized in that it is electrically connected to an input (E _n ) of an acquisition system (7, 7 ′) having a summing and amplifying function and comprising at least one operational amplifier (8). The current transformer according to any one of 1 to 4. The partial circuits (CB _n ) are identical, and each input (E _n ) of the acquisition system (7, 7 ′) is related

Is connected to the input (9) of the operational amplifier (8) through a resistor having a resistance value R ₁ selected to satisfy
Where α _Z is the temperature coefficient of sensitivity (S _n ) of the Rogowski coil formed by the winding (C _n ), and β constitutes the winding (C _n ) of the partial circuit (CB _n ) The temperature coefficient of the resistivity of the material to be used, and r ₀ is the internal resistance of the winding (C _n ) at a specific reference temperature (T ₀ ), and the signal from the complete circuit (CB) is 6. Current transformer according to claim 5, characterized in that once amplified by the acquisition system (7, 7 '), it is independent of changes in the temperature (T) of the transformer. . The current transformer according to claim 5 or 6, wherein the voltage signal (v _{s (n)} ) output by the partial circuit is added in phase by the acquisition system (7, 7 ').   8. A current transformer according to claim 1, comprising a plurality (p) of complete circuits (CB) arranged in parallel to one another. Including multiple (p) complete circuits (CB) arranged parallel to each other,
The acquisition system (7) includes an amplifier circuit including an operational amplifier (8) having one input (9) connected to each of the partial circuits (CB _n ) constituting the complete circuit (CB). The current transformer according to claim 6, wherein the current transformer is included. Including multiple (p) complete circuits (CB) arranged parallel to each other,
The acquisition system (7 ′) includes a first amplification stage (71, 72) including at least two operational amplifiers (8), and the output from each amplifier (8) of the first stage is the complete signal (v The current transformer according to claim 6 or 7, characterized in that it is connected to a second stage of addition provided for generating _s ).   The current according to claim 10, characterized in that the second adding stage comprises an operational amplifier (8 ') with a feedback loop for amplifying the sum of the signals generated by the first amplifier stage. Transformer.

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